DICOM Standard Browser

by Innolitics

Built with by Innolitics, a team of medical imaging software developers.

Data synced with official DICOM standard on 25 September 2017. The DICOM Standard is under continuous maintenance, and the current official version is available at http://dicom.nema.org/. DICOM Parts 3 and 6, © NEMA. Please note that the most recent PDF version of the standard is the official reference, and should checked when making technical decisions.

Exposure Time Attribute

Tag (0018,1150) Optional (3) ExposureTime 1 Integer String (IS)

Time of x-ray exposure in msec.

If Acquisition Type (0018,9302) equals SPIRAL, the value of this attribute shall be Revolution Time (0018,9305) divided by the Spiral Pitch Factor (0018,9311). See Section C.8.15.3.8.1 and Section C.8.15.3.2.1.

Section C.8.15.3.8.1

C.8.15.3.8.1 Exposure Time in ms Attribute (Informative)

An example of how the value of Exposure Time in ms (0018,9328) can be calculated:

The Exposure Time Texposuretime of a volume shall be the time of the X-Ray radiation in position with this volume. It depends on the travel speed and the total collimation width.

Texposuretime of the volume represented by a distinguished frame of a Spiral Scan can be calculated as follows:

Texposuretime = N x S / Vtravelspeed

CTpitchfactor = DD / N x S

Vtravelspeed = DD / Trevolutiontime

From this the exposure time can be derived:

Texposuretime = N x S x Trevolutiontime / DD = Trevolutiontime / CTpitchfactor

Legend:

DD = Table Feed per Rotation (0018,9310) in mm distance moved by the patient support in the z direction per 360° revolution in Spiral scanning

S = collimation of a single slice in mm

N = number slices

N x S = Total Collimation Width (0018,9307) in mm

Vtravelspeed = Table Speed (0018,9309) in mm/second, travel speed of the patient table

Trevolutiontime = Revolution time (0018,9305) in seconds

CTpitchfactor = Spiral Pitch Factor (0018,9311)

Section C.8.15.3.2.1

C.8.15.3.2.1 Acquisition Type

Defined Terms:

SEQUENCED

identifies that the acquisition was performed by acquiring single or multi detector data while rotating the source about the gantry while the table is not moving; additional slices may be acquired by incrementing the table position and again rotating the source about the gantry while the table is not moving

SPIRAL

identifies that the acquisition was performed by acquiring data while rotating the source about the gantry while continuously moving the table

CONSTANT_ANGLE

identifies that the acquisition was performed by holding the source at a constant angle and moving the table to obtain a projection image (e.g., a localizer image)

STATIONARY

identifies that the acquisition was performed by holding the table at a constant position and performing one or more acquisitions over time at the same location

FREE

identifies that the acquisition was performed while rotating the source about the gantry while the table movement is under direct control of a human operator or under the control of an analysis application (e.g., fluoroscopic image)